One of the most common cooking devices used is the deep fryer. Deep fryers are commercially used by restaurants, institutional kitchens, and fast food establishments for cooking a variety of food products, such as french fries, fish, chicken, seafood, etc. Deep fryers are also available for use in residential environments.
A deep fryer cooks food by totally immersing it within a vat or tank that is filled with heated oil or shortening (for ease of discussion, the heated oil, shortening, grease, or other heating agents used by the deep fryer will hereinafter collectively be referred to as "oil"). The oil may be heated by any suitable manner. For example, it can be heated by using a flow of heated gas that is forced or drawn through a heat exchanger having flow passages that are located within or external to the cooking vat. A gas burner is provided to heat the gas circulating within the heat exchanger. Likewise, it is also possible to use a deep fryer that is electrically heated.
While deep fryers provide the ability to cook a variety of foods in a convenient manner, they also create some unique safety hazards. In particular, deep fryer oil fires are not uncommon and can cause substantial damage to a restaurant, including destruction of the entire building the restaurant is in. Of course, and any fire situation there is substantial risk to individuals near the fire.
One reason why deep fryer fires are so dangerous is that there is a substantial amount of oil in the reservoir of the deep fryer, and the oil acts as a large fuel supply to continue the fire and potentially place restaurant employees and emergency personnel at risk. It would be desirable to have a method of preventing the reservoir of oil in a deep fryer from becoming a fuel supply for a fire.
In the fire extinguishing art, fires are divided into four general classes; namely, Class A, Class B, Class C and Class D.
Class A, C and D fires are not related to the type of fire found in the deep fryer. Class A fires involve combustible material such as paper, wood, etc. They are extinguished by quenching and cooling with large quantities of water or solutions containing a large percentage of water. Class C fires involve electrical equipment. This type of fire is extinguished with dry fire extinguishing agents. Class D fires involve combustible metals and are typically extinguished with special dry powders.
The instant invention is directed to class B fires which occur in deep fryers. Class B fires involve shortening, oils, greases, flammable liquids, etc. In this type of fire, water is typically not used because when the water contacts the hot oil, it may cause splattering without extinguishing the flames. In addition, when the hot oil splatters, hot burning oil may cause the fire to spread and may also cause serious injury to anyone standing nearby. Class B fires are difficult to extinguish because of the low auto-ignition points of deep fryer oil (which can be any number of shortening, oils and greases). As noted above, in addition to the low ignition temperature, the oil reservoir in the deep fryer contains a large amount of oil which acts as a fuel supply to feed the fire for a substantial period of time. The longer the fire is active, the greater the risk that the fire will spread. As a result, because of the large quantity of available oil typically found in a deep fryer, it is extremely important to extinguish the fire as rapidly, because the reservoir of oil can provide sufficient fuel supply for the fire to allow the fire to spread. In addition, even if the fire is extinguished quickly, there is a secondary fire hazard which can occur due to "reflash" (i.e. re-ignition of the fire because the oil remains above the ignition temperature after the flames have been extinguished) which can occur at a lower temperatures.
Attempts to extinguish class B fires have resulted in the development of many different fire extinguishing compositions and fire extinguishing systems which are designed to extinguish the oil fire while the oil remains in the deep fryer. While these extinguishing systems may be effective in putting out the fire, they can take a substantial amount of time which may result in substantial property damage or injury to individuals.
In addition, re-flash or auto-ignition of the hot oil in a class B fire remains a serious problem. Further, when such fires involve large commercial establishments, such as restaurants, cafeterias, mess halls, etc., the potential damage caused by such fires may be substantial. The prior art systems typically are directed to extinguishing the fire and are not directed to eliminating the fire's fuel supply which is represented by the oil reservoir of the deep fryer. It would be desirable to have an improved method of extinguishing a class B fire (the type which occurs in a deep fryer) which eliminates the fuel supply of the fire, and which simultaneously eliminates the splattering of the oil in the deep fryer reservoir and the risk of reflash.
In addition to the attempts to control and extinguish class B fires through the use of chemicals, prior art attempts to extinguish fires such as those found in the fryers have included mechanical devices. In particular, attempts have been made to smother deep fryer fires by covering the deep fryer with a fireproof blanket. This type of blanket may be deployed through the use of automatic machines that are controlled by fire sensors, or they may be manually thrown over the deep fryer. The use of manually deployed blankets can be hazardous since the individuals deploying the blanket must come close to the fire, exposing themselves to danger.
While addressing the basic desirability of extinguishing class B fires, the prior art has failed to provide a system which rapidly extinguishes fires in deep fryers by eliminating the fuel supply for the fire, which in turn eliminates the dangers caused by splattering that may occur while the fire is being extinguished, and which further eliminates the potential for reflash after the initial fire has been extinguished.